[docs] Fix Nav components subsections to be open by default

[mbrookes]

• I have followed (at least) the PR section of the contributing guide.

[mui-pr-bot]

Details of bundle changes.

Comparing: 6b73158...9e4f2d4

bundle	parsed diff	gzip diff	prev parsed	current parsed	prev gzip	current gzip
@material-ui/core	0.00%	0.00%	315,279	315,279	86,429	86,429
@material-ui/core/Paper	0.00%	0.00%	67,869	67,869	20,159	20,159
@material-ui/core/Paper.esm	0.00%	0.00%	61,152	61,152	18,952	18,952
@material-ui/core/Popper	0.00%	0.00%	28,740	28,740	10,351	10,351
@material-ui/core/Textarea	0.00%	0.00%	5,513	5,513	2,382	2,382
@material-ui/core/TrapFocus	0.00%	0.00%	3,744	3,744	1,581	1,581
@material-ui/core/styles/createMuiTheme	0.00%	0.00%	15,960	15,960	5,782	5,782
@material-ui/core/useMediaQuery	0.00%	0.00%	2,106	2,106	975	975
@material-ui/lab	0.00%	0.00%	138,336	138,336	42,572	42,572
@material-ui/styles	0.00%	0.00%	51,353	51,353	15,175	15,175
@material-ui/system	0.00%	0.00%	14,458	14,458	4,178	4,178
Button	0.00%	0.00%	84,061	84,061	25,579	25,579
Modal	0.00%	0.00%	20,344	20,344	6,685	6,685
colorManipulator	0.00%	0.00%	3,904	3,904	1,543	1,543
docs.landing	0.00%	0.00%	47,836	47,836	10,920	10,920
docs.main	0.00%	0.00%	654,121	654,143	205,688	205,697
packages/material-ui/build/umd/material-ui.production.min.js	0.00%	0.00%	294,254	294,254	83,882	83,882

Generated by 🚫 dangerJS against 9e4f2d4

[oliviertassinari]

That's not an easy one 😆⚖️ :

expect(document.querySelectorAll('.algolia-lvl0').length).toBe(1) // 🔥 KO

[oliviertassinari]

Just to clarify my previous message. It breaks the Algolia fix.

[mbrookes]

Oops, didn't realise the algolia logic was also broken. Hope I've correctly understood the desired output.

[oliviertassinari]

I believe the following solve your problem and mine. Let me know.